The present invention relates to coffee grinders and more particularly to such grinders which are used to grind roasted coffee beans in selected degrees of fineness.
At the present time, the advantages of freshly ground coffee are widely recognized, particularly in restaurants, cafes and other establishments. The advantages to the coffee roaster are that he may sell roasted beans in convenient containers, such as 5-lb. oxygen-barrier bags, and avoid the problems arising from in-plant grinding, such as environmental dust. He can also reduce packaging, warehousing and shipping costs.
Freshly ground coffee has numerous advantages to the restaurant. The brewed coffee, when made from freshly ground beans, has a superior aroma and taste compared to coffee brewed from previously ground beans. If the coffee has been pre-ground and packed, it is more likely to become stale and lose its flavor after the package has been opened. It is also inconvenient to utilize small pouches, such as the 2-3 oz. size, as they are subject to spillage and pilferage. In addition, it is considered by many restaurants to be more economical to grind the coffee themselves than to purchase ground coffee. Many restaurants want to advertise their coffee as being freshly ground and brewed.
There are a number of machines presently available for restaurants and other establishments which will grind a specified amount of coffee selected by the user. The coffee beans may be measured by their volume, by use of a timer, which may be inaccurate as to the final amount of ground coffee, due to the differences in density between batches of beans and other inaccuracies inherent in a timed system. In general, these machines consist of a rotatable disc cutter having extending blades which cut and grind the coffee beans between two rotatable discs in a one-stage grinding process. In many restaurants the coffee grinder may be used a number of times during the day, resulting in heavy usage and wear of the blades. The blades may be both time-consuming and expensive to replace or sharpen. In addition, the blades may give off an excessive amount of heat, damaging the coffee as it is being ground. In some cases the cutter may crush the beans instead of cutting them, which causes a build-up of heat, extraction of oils, and loss of flavor.
The presently commercially available machines produce a relatively uneven batch of ground coffee, that is, the particle size range may be relatively broad and, more importantly, the particle size is not uniform. The distribution of the sizes of particles may resemble, in statistical terms, a broad bell curve, so that many particles, at the right end of the imaginary particle size distribution curve, are large and their interiors not penetrated by the hot water. Much of the coffee flavor of such larger particles is unused and wasted.
It has been found, through the inventor's experimentation, that a greater amount of coffee may be brewed by using fine particles, which are of a uniform size, preferably, almost all of the particles (over 90%) are in the range of 200-300 microns in diameter and the particles are produced without crushing or pulverizing. It is believed that, under atmospheric pressure, the hot water from which the coffee is brewed penetrates each particle only a few cells deep from the surface, i.e., a layer of penetration of about 100-150 microns. A particle, which may be relatively large compared to the depth of hot water penetration, given up its coffee flavor only from a layer 3-5 cells thick on its surface. If a larger amount of surface area of the coffee bean can be exposed to the hot water, by decreasing the size of the particles and having uniformly sized particles, there will be an increase in the number of cups of coffee which can be successfully brewed from the same amount of roasted coffee beans. Presently, within the restaurant trade, it is considered that an acceptable amount of coffee to be produced from one pound of roasted beans is in the range of 55-75 cups, the lower end of the range providing stronger coffee.